The relevance of scapular dysfunction in neck pain: clinical features, kinematics, and muscle activity

Abstract

Scapular dysfunction has been demonstrated in patients with nonspecific neck pain. However, clinical characteristics of scapular dysfunction to neck pain remain unclear and need to be further investigated. The general aims of this thesis were 1) to investigate reliability of clinical assessments of scapular dysfunction in patients with nonspecific neck pain, 2) to determine characteristics of neck pain and scapular dysfunction in relation to neck pain 3) to investigate the behavior of the axioscapular (upper trapezius: UT, lower trapezius: LT and serratus anterior: SA) and neck extensor (NE) muscles during isometric shoulder tasks in patients with neck pain with scapular dysfunction. The first aim consisted of two studies (study I and II). Study I investigated inter-rater reliability and intra-rater (live vs video) of visual observation of scapular dyskinesis in patients with neck pain (n = 69). Two examiners categorized scapular dyskinesis on the side of neck pain during unilateral and bilateral arm elevation using simple (yes/no) and specific type (winging, dysrhythmia, mixed abnormality or normal) classifications. One examiner randomly reviewed the video recordings. The results demonstrated moderate to very good inter-rater and moderate to good intra-rater reliability (live and video) of visual observation for identifying scapular dyskinesis in neck pain patients. Study II evaluated reliability of manual scapular repositioning for changes in neck pain and rotation range and patients’ perceptions in patients with neck pain and altered scapular alignment (n = 69). Two examiners performed manual scapular repositioning on the side of neck pain. Neck pain intensity and rotation range were measured at baseline and during the modified scapular position. Response to scapular repositioning were defined as “improved” (changes in pain >2/10, range ≥7 degrees and much better for perception) and “no change”. The results demonstrated good reliability between examiners and moderate agreement between the measured changes and patients’ perception. The second aim consisted of three studies (study III, IV and V). Study III investigated clinical characteristics of patients with neck pain who responded and did not respond to scapular repositioning in patients with neck pain and altered scapular alignment (n = 144). Clinical characteristics were neck pain intensity, duration, disability, headache, type of scapular dysfunction, cervical musculoskeletal impairment (range of motion, flexion rotation test and symptomatic cervical joint dysfunction), upper limb functional limitation and self-reported disability. Manual scapular repositioning was performed on the side of neck pain. Change scores in neck pain intensity and rotation range were used to define responsive and non-responsive participants. The results showed that 107 participants responded and 37 did not respond to the scapular repositioning. The responsive group had the presence of headache, scapular downward rotation and upper cervical spine dysfunction while the non-responsive group had scapular protraction and lower cervical spine dysfunction (p < 0.05). Study IV investigated clavicular and scapular orientations and identify subgroups of neck pain patients in patients with neck pain and altered scapular alignment (n = 58). The scapular orientations were measured on the side of neck pain. Cluster analysis identified two subgroups of neck pain: subgroup 1 with greater clavicular retraction and scapular downward rotation (SDR) and subgroup 2 with greater clavicular elevation, scapular internal rotation, and anterior tilt. Subgroup 1 had higher incidences of headache, more pain in upper neck and positive responses to scapular repositioning (p < 0.01). Subgroup 2 had more pain in lower neck and no response to scapular repositioning (p < 0.01). Study V investigated clavicular, scapular, and spinal kinematics in patients with neck pain with observed (i) scapular winging, (ii) scapular dysrhythmia, (iii) no scapular dyskinesis and asymptomatic controls (n = 20 in each group). The kinematics data was measured during unilateral arm elevation and lowering at 30°, 60°, 90°, and 120°. The results showed that the neck pain group with scapular winging had decreased clavicular retraction and increased scapular internal rotation and anterior tilt and those with scapular dysrhythmia had decreased scapular upward rotation (p < 0.01). The third aim included one study (study VI). Study VI investigated the behavior of the axioscapular (UT, LT and SA) and NE muscles during isometric shoulder tasks in patients with neck pain with SDR, those with no scapular dysfunction and asymptomatic controls (n = 30 in each group). Electromyographic signals were recorded unilaterally from the UT, LT, SA and NE during isometric shoulder 30°flexion, 30°abduction and 30°external rotation at 20%, 50% and 100% maximal voluntary contraction (MVC). The results revealed that the neck pain group with SDR had increased UT activity and UT/LT and UT/SA ratios at low load tasks (20% and 50% MVC) in shoulder flexion and abduction (p < 0.05). The neck pain group with and without SDR had greater NE activity in all tasks (p < 0.001). In conclusion, this thesis provides evidence for clinical assessment and nature of the scapular dysfunction in patients with neck pain. Visual observation is a reliable tool for screening scapular dyskinesis and manual scapular repositioning is a reliable tool for identifying scapular dysfunction in relation to neck pain. Scapular dysfunction is common, but not necessary to be related to neck pain in all cases. Altered scapular kinematics and muscle activity are influenced by type of scapular dyskinesis. The overall results suggest that patients with neck pain with scapular dysfunction should not be regarded as a homogenous group. Benefits for the patient may be gained if the scapular dysfunctions are addressed with specific exercise strategies in management.